1. Field of the Invention
The present invention relates to a seat belt retractor provided in a vehicle such as an automobile in order to retract and unreel a seat belt using a driving force from a motor.
2. Description of the Related Art
Conventionally, a vehicle seat is provided with an occupant restraining seat belt device for preventing an occupant from moving forward due to an inertial force when large deceleration acts on the vehicle, for example when the vehicle stops suddenly or crashes.
The seat belt device is provided with a retractor for retracting and unreeling the seat belt. In order to retract the seat belt without slack or looseness, the retractor unwinds or retracts the seat belt in accordance with movement of the occupant, thereby remaining in close contact with the occupant. During an emergency, such as a sudden stop or a crash, the retractor prevents the seat belt from unreeling, and as a result, the occupant is restrained.
In recent years, retractors including a motor, i.e. so-called electric retractors, have become common. An electric retractor retracts and unreels the seat belt using a driving force from the motor, thereby leading to improvements in occupant safety and user-friendliness.
An example of such an electric retractor is disclosed in Japanese Patent Application Publication No. 2005-297676, in which a webbing retraction device having a simple structure which allows variations in retraction characteristics to be set easily. Further, Japanese Patent Application Publication No. 2008-018815 discloses a motor retractor and a seat belt device employing the motor retractor with which working efficiency can be improved by facilitating electric connection between a harness assembly and a motor terminal and an assembly operation of the harness assembly.
FIG. 8 is a view showing an example of a conventional seat belt retractor. A conventional seat belt retractor 10 (hereinafter referred to as the retractor 10) includes a gear case 11 comprising a gear case upper portion 11a and a gear case lower portion 11b, a plurality of gear members 12 having a gear that is housed in the gear case 11, a motor 14, a motor front case 13 housing the motor 14, an O ring 15 serving as a waterproofing member, a motor rear case 16, a harness connection member 17, a harness 18, and a motor rear cap 19.
As described above, an electric retractor has many advantages. However, use of a motor leads to increases in the number of necessary components, the number of processing steps, and the manufacturing cost. It is desirable to achieve a reduction in manufacturing cost.
Reducing the number of components is one of the most effective ways of reducing the manufacturing cost, however, measures must be taken to ensure that defects and so on do not occur as a result. In particular, sufficient measures must be taken to ensure a waterproof property of the motor case housing the motor and the connection between the motor and the harness that supplies the motor with power, i.e. in areas where defects are most likely to occur.
More specifically, when water infiltrates the motor interior, the motor is likely to malfunction, and therefore a high degree of waterproofing is required of the motor case housing the motor. In the motor retractor described in Japanese Patent Application Publication No. 2008-018815, for example, infiltration of water or the like through the rear side of the motor is prevented by a motor seal ring (also referred to as an O ring) and a grommet. Further, in this motor retractor, an opening portion is provided in the motor cover, and therefore measures must also be taken to prevent water infiltration through this part (the front side of the motor).
When a connection defect occurs between the motor and the harness, the motor cannot operate correctly, and therefore a reliable connection is required in the connecting part between the motor and the harness. In the webbing retraction device described in Japanese Patent Application Publication No. 2005-297676, for example, the harness is wound around the periphery of the retractor and may therefore be pulled unintentionally when attaching the retractor to a vehicle body, thereby leading to a connection defect between the motor and the harness.